High Street JUMP Raingardens Project

Raingardens are special types of garden beds that are designed to collect and filter stormwater run-off from hard surfaces such as streets, driveways, paving and gutters.

The High Street, JUMP raingardens are low-lying with high edges surrounding them, letting stormwater that flows down the steep streets in this area to slow down and pool on the surface before soaking through to the plant roots and soil layers.

Each raingarden is planted with native plants and grasses that can survive long periods of time without rain, and inundations (floods) at other times. These plants have deep, fibrous (hairy) and spreading root systems, that are good at taking up water and nutrients that pass through the soil.

A layer of large pebbles on the surface of each garden and pit helps to trap litter and sediment (small particles of soil and silt).

Below the raingarden and tree pit surfaces, layers of soil, sand and bioretention media (a special soil mix designed to filter out pollutants) work to clean stormwater. Layers of sand and gravel also help drain water to the lower levels. Larger particles are generally trapped in the top layers, with smaller particles trapped in the lower levels. At the lowest level is a layer of crushed rock laying over a slotted pipe, where the cleaned, filtered water can exit the raingarden and drain to the nearby Merri Creek.

How a raingarden works

Gravity System: The raingardens use gravity to capture stormwater in the garden beds. The rainwater is collected via runoff from the steep roads and gutters in the area. The location of the raingardens was an important design consideration in this project.

Top layer: Deep rooted plants such as kangaroo paw, sedges, club rush, hollow rush, mat rush and cushion bush.

Middle layers: Boulders, gravel mulch, bioretention media.

Bottom layer: Crushed rock laying over a slotted drain connected to stormwater system.

Overflow Pit: An area for excess water to flow into when there is heavy rainfall, preventing flooding of the gardens.

2014
‘Junction Urban Master Plan: from Pavement to Place’ developed.

2016
‘High St Renewal Project Plan’ construction stages completed, including kerb extensions and garden beds.

2017
Raingarden project construction completed.

Maintenance tasks include:
• Weeding and replacement of plants as needed.
• Monitoring how long it takes for water to filter through the raingarden to ensure the system is working.
• Replacing the substrate (layers of gravel and soil) when required.

The Junction Urban Master Plan was developed by Council in partnership with the community to improve the attractiveness and liveability of the public spaces and streetscape of the Preston Junction. The installation of raingardens demonstrates City of Darebin’s commitment to sustainable design and a healthier environment.

The Preston Junction precinct is a fast-growing local area. New residential and business developments have been built and many more people are now visiting the area. The raingardens improve the streetscape and increase biodiversity in the area as well as reducing the risk of flooding, by re- routing some of the stormwater that would normally flow into the stormwater system. The raingardens provide a smart and sustainable environment to be enjoyed by residents and visitors.

Signs near the raingardens also help educate the community about stormwater management. They help us understand how litter, silt, oils, chemicals and other pollutants can be filtered out of stormwater to improve water quality in our waterways. This helps us to see the connection between our community and natural environment.

Many animals and insects call our local creeks and waterways home. The platypus, rakali (native water rat), water bugs, frogs, fish and birds (such as the sacred kingfisher) are all found in Darebin waterways.

When it rains, pollutants washed from our streets end up in the waterways. These pollutants include those we can see (such as plastics and cigarette butts) and those we can’t see (such as oils, detergents, bacteria and pesticides). Pollution of our waterways has a negative health impact on our local aquatic wildlife and plants.

Raingardens clean, filter and separate water from pollutants, before it enters our creeks, rivers and ultimately the ocean. Raingardens also help to slow down the speed that stormwater enters our waterways, reducing problems of erosion (loosening of soil) on creek banks. Slowing the speed at which water enters our waterways helps to improve our overall stream water quality.

Protecting our local water ways is an important environmental benefit. Raingardens create healthier and cleaner waterways for all.

Raingardens also improve the streetscape of an urban environment. They introduce plants and birds to areas that are mainly concrete, roads and buildings. Increasing plants, trees and soil in an area can also help to absorb excess heat and provide shade (improving the microclimate).

Darebin City Council acknowledges the Wurundjeri people as the traditional owners and custodians of this land and pays respect to their Elders past and present.

Artwork infographics developed and supplied by City of Melbourne. For other examples of WSUD Urban stormwater treatment projects visit the City of Melbourne Urban Water interactive map here.

This project is part of Melbourne Water’s Water Sensitive Urban Design (WSUD) program.

A portion of the funding for the project was provided by Melbourne Water’s Living Rivers Grant.